The present invention relates generally to a roll feed unit for feeding a continuous web of material from a roll to a sheet fed printing device such as a conventional sheet fed laser printer. In combination, the roll feeding unit and printing device provide an integrated assembly that is used to feed, print, and cut the continuous web material. The roll feeding unit can be used to feed a continuous web of print media such as, for example, a web of banner paper or a web of adhesive-backed paper. In other instances, the roll feeding unit can be used to feed a continuous web of carrier material carrying distinct image-receiving media items such as, for example, pressure-sensitive adhesive labels. In all cases, the printer produces a toner image on the web as it is fed through the printer. At the end of the printing operation, the web is cut to produce a finished roll of printed media or a finished roll of printed labels that are ready for application to packages, containers, and other articles.
One of the important concepts of the invention is to provide a roll feed assembly which functions to retrofit a conventional sheet fed laser printer so that it can operate as a continuous feed printer. A conventional laser printer includes an image transfer assembly, which transfers a toner image from an imaging belt or drum to a single sheet of paper, as the paper is fed through the printer. The feed rate of the paper is synchronized with the print drive of the printer so that the paper is fed to the imaging belt or drum at the time when the image is ready to be printed on the paper. The image is transferred to the paper, and a fixing unit in the printer fixes the image on the paper. This results in a generally high-quality printed image being produced on the paper. However, one drawback to conventional laser printers is that they are generally designed to accept only stacked, pre-cut sheets of paper. It would be desirable to provide a system that could feed a continuous roll of paper, rather than individual sheets, to a conventional laser printer. Such a system would be more efficient and economically advantageous in many applications. For example, the system could be used for on-demand printing of individual labels that are carried on a continuous roll of paper or other web material.
The industry has previously attempted to address the feeding of a continuous roll of paper to a laser printer in a number of ways. For example, Estabrooks, U.S. Pat. No. 5,768,675 (“Estabrooks '675”) discloses an on-demand electrophotographic printer for printing an image on a continuous web being fed from a roll. The Estabrooks '675 printer includes an internal feeding and cutting mechanism integrated into the printing device itself for feeding a continuous roll of media through the print engine.
In one embodiment of Estabrooks '675, the front edge of the paper web is sensed by a detector. Then, the speed of the image carrier drum in the printer is accelerated. The paper feed stepper motor is synchronized so that it accelerates to the same speed as the drum, and the paper is fed to the point where the image can be precisely transferred to the paper. At the end of the printout, the drum stops rotating, while the paper feed motor slows the web speed and stops the web at a cutter for cutting the printout. A controller then reverses the paper feed motor, returning the cut edge of the paper web to the start position, where it awaits the start of the next print cycle. Thus, Estabrooks '675 solves the problem of printing on a continuous paper web with an integrated roll feeding assembly located within the printer. There is no external roll feeding unit for feeding the paper web to the printer. Furthermore, in Estabrooks '675, the paper web is cut after each printout by a cutting mechanism within the printer. Then, the front edge of the paper, which has just been cut, is retracted to a start position in front of the image carrier drum within the printer, and a new printing cycle begins.
Estabrooks, U.S. Pat. No. 5,633,740 (“Estabrooks '740”) also discloses an on-demand media web electrophotographic printer containing an integrated feeding and cutting assembly. This apparatus also can be used for printing tickets, tags, barcodes, and labels on a paper web. The apparatus includes a system for monitoring and controlling the web feeding, registration, and cutting of the web by utilizing a sensor system. The sensor system includes a web buckle sensor that senses whether or not a web buckle has been formed prior to each feeding and cutting of the web. A central processor commands the feed roll unit to advance the leading edge of the web so that the edge is detected and stopped at a registration roll nip. With the leading edge of the media web positioned correctly, the processor feeds the edge of the web against an upper registration roll and web guide to form a web buckle. According to Estabrooks '740, the web buckle is necessary to allow time for a clean cut of the web to occur, but its length is small enough to avoid feeding jams. Thus, Estabrooks '740 solves the problem of printing on a continuous roll of paper with an integrated roll feeding assembly located within a printer.
Although the roll feeding systems described in the foregoing Estabrooks '675 and '740 patents may be effective in some instances, it would be desirable to have a new system which uses an external roll feeding unit for feeding a continuous roll of web material to a printer. The external roll feeding unit provides several advantages in terms of cost and ease of use. For example, by providing an external roll feeding unit that serves to retrofit an existing laser printing device, the costs of redesigning the basic printing unit are saved, and the efficiencies and low costs of conventional laser printing devices are retained. Further, it is easier to load and reload the roll of web material, and to service the roll feeding mechanisms in an external roll feeding unit versus an internal roll feed that is housed within the printing unit.
The present invention provides such a new feeding, printing, and cutting system. The web roll feeding apparatus of the present invention is an external unit that supports and feeds the web to the printer. The assembly of this invention includes a roll feeding unit, a cutter, a printer unit, a roll feeding unit controller, a printer controller, and various sensors for synchronizing the feeding, printing, and cutting of the web. These and other objects, features, and advantages of this invention are evident from the following description and attached figures.